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김형국(Hyung Kuk Kim),이동규(Dong Gyu Lee),백종현(Jong Hyeon Peck),강채동(Chaedong Kang) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.9
A numerical analysis of solid-liquid phase change was performed on a heat transfer module which consisted of circulating water path (BRINE), heat transfer plate (HTP) and phase change material (PCM) layers, such as high temperature PCM (HPCM, 78~79℃) and low temperature PCM (LPCM, 28~29℃). There were five arrangements, consisting of BRINE, HTP, LPCM and HPCM layers in the heat transfer module. The time and heat transfer rate for melting/solidification was compared to their arrangements, against each other. As results, the numerical time without convection was longer than the experimental one for melting/solidification. Moreover, the melting/solidification with the BRINEⅠ-LPCM-BRINEⅡ- HPCM arrangement was faster(10 hours) than the others; HPCM-BRINE-LPCM, BRINEⅠ-HPCM-LPCM-BRINEⅡ one.
김형국(Hyung-Kook Kim) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.6
A plastic noise barrier is a structure installed to minimize noise, and it is composed of the main plate, sound-absorbing plate, and sound-absorbing material. Plastic noise barrier structures have several advantages compared to other products, such as light weight, anticorrosion, durability, easy assembly, rapid construction, and low costs. In this study, the main and sound-absorbing plates were manufactured through extrusion molding, and the sound-absorbing plate was finished with a press to improve the conventional injection molding. Extrusion molding dies and punch dies were designed, and a profile extrusion-molding system was developed. Thus, inexpensive and efficient sound-absorbing and main plates can be produced, and the noise barrier structure can be assembled rapidly. Additionally, a noise barrier structure with extended service life and excellent quality can be constructed by creating uniform free space to accommodate increased temperatures after assembly and installation.
김형국(HyungKuk Kim),김경훈(KyungHun Kim),백종현(JongHyeon Peck),강채동(Chaedong Kang) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
Phase change material(PCM) is applied actively to a supplementary heat source/sink in building HVAC and others.In order to show that thermal interference of adjoining two PCMs which made two rooms. Two PCMs, the high temperature PCM(HPCM, M.P: 78~79°C) and low temperature PCM(LPCM, M.P.:28~29°C) were utilized to the thermal energy storage material. PCMs were charged in two rooms of module, respectively. The arrangement of the cell was selected to BRINE-HTPCM-LTPCM order which was found to the worst heat transfer rate during melting/solidification from previous study. In this study, we predicted the heat transfer rate of HTP to that of HTP with perforated fin(FHTP) using CFD. We compared using CFD results and experimental results. At results, melting/solidification time of CFD results is long compared to the experimental results. But results of FHTP was shorter than results of HTP.
김형국(H. K. Kim),최병철(B. C. Choi),김민국(M. K. Kim),최재혁(J. H. Choi),정석호(S. H. Chung) 한국연소학회 2008 KOSCOSYMPOSIUM논문집 Vol.- No.-
The effect of AC electric field on flame position in counterflow burner has been investigated experimentally by varying the voltage and frequency. The result showed that the flame position maintained the typical flame shape above critical frequency, which was stable regardless of applied voltage amplitude. In contrary, below critical frequency, the flame position was oscillated. The oscillating flames were categorized in two regimes. For high frequency regime from 2 ㎐ to critical value, the flame position was sinusoidally oscillated with increasing amplitude as applied voltage amplitude increases. And for low frequency regime below 2 ㎐, the flame position was complicatedly oscillated with peak phenomenon having rapid variation of the position. In such a case, the low frequency oscillating flames were controlled by interaction between the flame position variation on DC electric field and the chemically response time on AC electric field.
김형국(Hyung-Kook Kim) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.8
This study investigates the injection molding of a plastic rack gear and focuses on deflections in the part. The causes of deflections were found and resolved through a trade-off study by injection molding analysis. Based on a warpage analysis, the fiber orientation was found to be a dominant factor in the occurrence of deflections. Changes in the part design and various injection conditions were analyzed for their effects in reducing deflections. Based on the trade-off study, a new part bottom design, injection time, and melt temperature were recommended. A trial injection was done for the new plastic rack gear, and measurements showed that its flatness surpassed that of the original part and met the specified requirement. The short injection time, low melt temperature, and symmetric similar configuration of the part contributed to the reduction in deflections. Therefore, optimized gate design and injection conditions as well as a new part design were validated through injection molding analysis in this study.
김형국 ( Hyeong Guk Kim ),구본학 ( Bon Hak Koo ) 한국환경복원기술학회(구 한국환경복원녹화기술학회) 2010 한국환경복원기술학회지 Vol.13 No.6
This study was surveyed to identify changes of flora during three years after restoration in Cheonggyecheon stream. There are four sections in Cheonggyecheon. One and two sections are upper streams and three and four sections are down streams. It was surveyed 328 species in 2006. In 2007 and 2008, 446 and 444 species were found, respectively. This result shows that Cheonggyecheon is unstable initial condition in restored stream ecosystem. Naturalized species were 58 species in 2006 and it was respectively 61 and 63 species in 2007 and 2008. Hazard species of ecosystem were three common species during survey period. In appearance of flora per section, three and four sections constituted by natural sites such as point bars, wide flood plains, riffles and ponds, marshes, etc. were surveyed more species than one and two constructed by concrete materials and narrow flow channel. Recently, as time goes by, introduced species are being increased. And succession has mainly been progressed by one year or binary herbs and perennial herbs. Corresponding author:Koo, Bon-hak, Dept. of Environmental Landscape Architecture, Sang Myung University, Cheonan 330-720, Korea, Tel:+82-41-550-5300, E-mail:ecoculture@smu.ac.kr Received:11 November 2010. Revised:8 December 2010. Accepted:20 December 2010. - 107 - Compared with other restored streams, Cheonggyecheon showed more flora than Yangjaecheon and Anyangcheon. It is judged owing to length of surveyed site, various planted species and area of inhabitation space. To manage restored stream ecosystem, monitoring is essential. Further, because change of vegetation after restoration in Cheonggyecheon is very important, continuous monitoring about Flora and Naturalized species and Hazard species of ecosystem is also very important.
김형국(Kim, Hyung Kook),조군제(Cho, Kun Je),조문영(Cho, Moon Young) 영남대학교 산경연구소 2012 영상저널 Vol.4 No.2
본 연구는 Jones모형, Jones_ROA모형, 수정Jones모형, 수정Jones_ROA모형을 통한 재량적 발생액을 각각 주정하였다. 이렇게 추정된 4가지의 재량적 발생액의 설명력을 비교 분석하기 위하여 F-Ratio를 사용하여 종속변수가 다른 모형들의 설명력을 비교해 보았다. 본 연구의 연구결과를 살펴보면, 종속변수가 Joens모형의 재량적 발생액(J-DA)과 Jones_ROA모형의 재량적 발생액(JR-DA), 수정된Jones모형의 재량적 발생액(J-DA)과 Jones_ROA모형의 재량적 발생액(AJR-DA)을 수정된 R²의 값으로 설명력을 검증한 결과 AJR-DA>JR-DA>AJ-DA>J-DA 순으로 나타났으며, F값 또한 수정된 R²와 같은 결과가 나타났다. 그리고 F-Ratio를 사용하여 재량적 발생액의 설명력을 비교하였으나, 두 시장 모두에서 유의수준에는 들지 못하는 것으로 나타났다. 이는 본 연구에서 측정된 재량적 발생액의 추정치는 차별성 없이 사용될 수 있다고 결론지을 수 있다. This study is conducted to look into the effects of LEV, GR, SIZE, FO and AQ that corporate characteristic variables on the quality of profit with dependent variables of discretionary accruals(DA) of Jones" Model, Jones-ROA Model, Adjusted Jones" Model, and Adjusted Jones-ROA Model by targeting companies that had been continuously listed on KOSDAQ from 2005 and 2009. This study aims to compare explanation of KOSPI and KOSDAQ regarding each model. the comparative result of each model"s explanation is not significant among all of the models. This explains that none of models has explanation.